Technical Field
The present invention relates generally to semiconductor devices, and more specifically, to multiple work function devices using a germanium oxide/titanium nitride (GeOx/TiN) cap on a work function setting metal.
Description of the Related Art
There is great difficulty in maintaining performance improvements in devices of deep submicron generations. Thus, methods for improving performance without scaling down dimensions have become of interest. There is a promising avenue toward higher gate capacitance without having to make the gate dielectric thinner. This approach involves the use of high-k materials. The dielectric constant of such materials is higher than that of silicon dioxide (SiO2). A high-k material can physically be thicker than an oxide and still have a lower equivalent oxide thickness (EOT) value.
High performance small field effect transistor (FET) devices are in need of precise threshold voltage control. As operating voltage decreases, threshold voltages also have to decrease, and threshold variation becomes less tolerable. Every new element, such as a different gate dielectric, or a different gate material, influences the threshold voltage. Techniques exist to tune device thresholds through the modification of the gate work function.